There are many references concerning polymeric enteric coatings. U.S. Pat. No. 3,524,910, Aug. 18, 1970 to Holliday et al. disclosed analgesic compositions wherein the analgesic (e.g., aspirin) is coated with ethyl cellulose in a weight amount relative to the amount of analgesic of from 1:22 to 1:50. U.S. Pat. No. 3,656,997, Apr. 18, 1972 to Cordes discloses analgesic containing gelatin capsules having a first coating of an enteric material. U.S. Pat. No. 3,691,090, Sept. 12, 1972 to Kitajima et al. discloses a method of encapsulating aspirin cores with an enteric polymer. U.S. Pat. No. 3,906,086 Sept. 16, 1975 to Guy et al. discloses a particle having an aspirin core and an enteric phthalate coating. U.S. Pat. No. 4,308,251, Dec. 29, 1981 to Dunn et al. discloses aspirin tablets containing aspirin, an enteric material and an erosion promoting agent such as corn starch.
Additional references disclosing coatings on analgesics include U.S. Pat. No. 2,953,497, Sept. 1960 to Press which discloses analgesic granules having a cellulose acetate phthalate coating; U.S. Pat. No. 3,166,476, Jan. 19, 1965 to Lowey which discloses aspirin particles which have a first coating of a material such as gelatin and a second enteric coating; British Pat. No. 1,129,811, Oct. 9, 1968 to Aspro-Nicholas Ltd. which discloses aspirin particles which have a coating of a polysalicylide and possibly a second,unspecified, coating.
Although the use of enteric polymers as disclosed in the above references provide for some stomach protection and release of the drug in the intestines, they are not the final answer. For chronic users of a drug like aspirin minimizing or eliminating stomach damage is a must and this is not achieved by the enteric polymers. The enteric polymers are "pH triggered" and are designed to be distrupted at the pH's found in the intestines, 5-7.5. However, even in the stomach where the pH of the gastric juices is acidic and the enteric should remain intact, most of the stomach muscosal, gastric lining has a higher pH and the enteric coating can be disrupted with stomach irritation the result.
The present invention involves the use of lipids which are not triggerd by pH (acidic or neutral) but are broken down by secretions, from the liver and pancreas, in the intestines. Lipids have been used to coat a variety of drug actives but not in the manner of the present invention.
The use of lipids in many prior references was to provide a sustained release of the drug. U.S. Pat. No. 2,921,883, Jan. 19, 1960 to Reese et al. discloses a mixture of a lipid (e.g., glyceryl tri-dihydroxystearate) and a cellulose derivative to provide a sustained release of the medicament. The pantentees distinguish their release from that given by an enteric coating. U.S. Pat. No. 3,147,187, Sept. 1, 1964 to Playfair discloses a drug mixed with a fat (e.g., glyceryl tristearate), and a swellable gum or proteinaceous material. U.S. Pat. No. 4,483,847, Nov. 20, 1984 to Augart discloses a sustained release composition comprising a mixture of high and low melting point lipids and the active ingredient. The intent of the patente was to achieve sustained release in the gastrointestinal system.
While the prior art discloses a variety of polymric enteric coatings and lipids, the use of lipids to provide an enteric coating of the type of the present invention has not been disclosed. The present inventors have found that a particular lipid coating provides for release in the intestines while minimizing or eliminating release in the stomach.
It is therefore an object of the present invention to provide therapeutic granules which have a more efficient enteric coating.
It is a further object of the present invention to provide theraputic granules which have a coating consisting of a mixture of lipids.
It is still a further object of the present invention to provide a method for treating pain, fever, and inflammation.
These and other objects will become readily apparent from the detailed description which follows. All percentages and ratios herein are by weight unless otherwise specified.